1. Field of the Invention
This invention relates generally to a combustion gas powered tool, and specifically to a combustion gas powered fastener driving tool such as a combustion gas powered tacker or nailer.
2. Description of the Prior Art
U.S. Pat. No. 4,403,722 discloses a combustion gas powered fastener driving tool which includes a movable piston and a gas combustion system for powering the piston. In this tool, the piston is moved by exploding gas. A fastener driver carried on the piston is actuated in accordance with movement of the piston. The gas combustion system has an air and fuel mixture exploding chamber in which blades of a fan are disposed. The fan allows the air and fuel to thoroughly mix, thereby insuring rapid mixture combustion. In general, the rapid mixture combustion enhances the power output characteristic and the efficiency of the gas combustion system.
In the tool of U.S. Pat. No. 4,403,722, the fan is driven by an electric motor partially disposed within the mixture exploding chamber. Since the fan and a portion of the electric motor are disposed within the mixture exploding chamber, they are exposed to high temperatures resulting from the combustion of the air and fuel mixture. These high temperatures tend to adversely affect the fan drive motor. Specifically, the high temperatures tend to deteriorate lubrication of bearings of the motor and tend to cause a breakdown of electrical insulation of the motor. Accordingly, this tool has a problem in durability.